WASHINGTON (AP) — The Justice Department has filed the first criminal charges in the deadly attack on the U.S. diplomatic mission in Benghazi, Libya, news reports said Tuesday.

CNN, NBC News and The Wall Street Journal reported that unspecified counts had been filed and sealed in the September 2012 attack that killed Ambassador Chris Stevens and three other Americans. CNN said the charges named Ahmed Abu Khattalah, a Libyan militia leader. The Journal said charges were filed against more than one person.

“The department’s investigation is ongoing. It has been, and remains, a top priority,” said Justice Department spokesman Andrew C. Ames, who declined to comment further.

A key Republican urged the administration to do more than file charges.

“Osama bin Laden had been criminally charged long before the Sept. 11, 2001, terrorist attacks but was not apprehended,” Rep. Darrell Issa, R-Calif., the chairman of the House Oversight and Government Reform Committee, said in a statement. U.S. Navy SEALS killed bin Laden in Pakistan on May 2, 2011. “Delays in apprehending the suspected Benghazi killers,” Issa added, “will only put American lives at further and needless risk.”

The Associated Press reported in May that American officials had identified five men who might be responsible for the Sept. 11, 2012, attack in Benghazi that occurred just weeks before President Barack Obama’s re-election. The FBI released photos of three of the five suspects, asking the public to provide more information on the men pictured. The images were captured by security cameras at the U.S. diplomatic post during the attack, but it took weeks for the FBI to see and study them. The FBI and other U.S. intelligence agencies identified the men through contacts in Libya and by monitoring their communications. They are thought to be members of Ansar al-Shariah, the Libyan militia group whose fighters were seen near the U.S. diplomatic facility prior to the violence.

Waiting to prosecute the suspects instead of grabbing them now could add to the political burden the Benghazi case already has placed on Obama and Democrats who want to succeed him in 2016.

Since Obama’s re-election, Republicans in Congress have condemned the administration’s handling of the matter, criticizing the level of embassy security and questioning the talking points provided to U.N. Ambassador Susan Rice for her public explanation of the attack. Conservatives have suggested that the White House tried to play down the incident to minimize its effect on the president’s campaign.

Republicans also have taken political aim at Hillary Rodham Clinton, who was secretary of state at the time of the attack and is a possible Democratic presidential contender in 2016.